The article I found indicated that 3mg of sabutamol is an optimal dosage. It's apparently available in a variety of dosages. The issue the authors were interested in was a good dosage that produced the bronchodilator effects they wanted without the tachycardia often associated with albuterol and its cousins.

i'm on sabutamol 5mg/2.5ml

There are lots of meds that can be nebulized, so you need to be specific regarding what med you're talking about.